Hydraulic variable speed transmission and method for operating the same



Jan. 12, 1937: 5 1 2,067,793

HYDRAULIC VARIABLE SPEED TRANSMISSION ANI METHOD-FOR OPERATING THE SAME Filed Oct. 7, 1953 v 4 Sheets-Sheet 1 Fig. 1

E. SEIBOLD 2,067,793

HYDRAULIC VARIABLE SPEED TRANSMISSION AND METHOD FOR OPERATING THE SAME Jan. 12, 1937.

Filed Oct. 7, 1955 4 Sheets-Sheet 2 Jan. 12, 1937. E. SEIBOLD 2,067,793

HYDRAULIC VARIABLE SPEED TRANSMISSION AND METHOD FOR OPERATING THE SAME Filed Oct. 7, 1933 4 Sheets-Sheet 3 Jan. 12, 1937. v E E OLD 2,067,793

HYDRAULIC VARIABLE SPEED TRANSMISSION AND METHOD FOR OPERATING THE SAME Filed-Oct. 7, 1953 4 Shets-Sheet 4 luvewran ATTURNEY Patented Jan. 12, 1937 UNITED STATES PATENT OFFICE HYDRAULIC VARIABLE SPEED TRANSMIS- SION AND METHOD FOR OPERATING THE SAME Ernst Selbold, Heldenheim-on-the-Brenz, Germany, assignor to J. M. Voith, Heidenheim-onthe-Brena, Germany, a co-partnership composed of Walther Voith, Hermann Voith, and

Hans Voith Application October I, 1933, Serial In Germany October 11, 19 2 15 Claims. (CI. 60-54) This invention relates to hydraulic variable speed transmissions and methods for operating the same, and more particularly to improvements in such transmissions as are generally known as the Foettinger type. Particular reference is herethe invention consists of an hydraulic variable speed transmission which has continuously open discharge apertures, which transmission is put in operation by supplying liquid thereto, and which is made inoperative by stopping the supply of 0 by made to my copending application Serial No. liquid; and/or in which the overflow edge of 688,727, filed in the United States Patent Ofllce the reservoir for the liquid lies deeper than the on September 9, 1933. deepest point or the rotating parts of the trans- The hydraulic variable speed transmission mission and/or in which the supply pump is 10 hereinafter referred to is one which comprises a placed at the lowest point of the reservoir. The 10 self-contained hydraulic torque changer which invention also consists of the new step in the may also be combined with a hydraulic slip couart in which the transmission is put in operation pling. The transmission is operated by emptying by the running or operation of the supply pump, or filling its various parts. w and put out of operation by stopping said pump.

This invention embodies such an hydraulic The second feature of the invention is to place 15 transmission, which is set in operation by filling the parts can'ying the liquid, which are necessary it with liquid, and put out of operation by intor the operation of the hydraulic transmission, terrupting the liquid supply. This invention all into the reservoir, built as a unit with the serves also to 'control the supply and distribution transmission. Another embodiment thereof conof the operating liquid. It may be mentioned sists in driving the supply pump from the pri- 20 here that heretofore in hydraulic transmissions mary shaft of the transmission. Another object which are set in operation by filling with liquid of this invention is to overcome certain disadvanand put out of operation by the interruption of tages of former devices, and this is accomplished the liquid supply and discharge of the operating by uniting the various elements for the liquid liquid through apertures (as for instance, clearsupply and its control into a single casing. This 25 ances between various elements of. the transmisarrangement brings about a great saving of space, sion), a return pump immediately carries the prevents outward leakage, and thereby increases liquid to an elevated reservoir, out of which the the safety of operation of the entire apparatus. transmission is supplied, as the demand requires The third feature of the invention consists in 3 with the aid of throttling elements. The return providing means to make possible the equalizapump runs in such a case, continually with the tion of pressure between the air spaces 01 the same speed of revolutions. The transmission is transmission and the reservoir, and to so place then controlled by means of the adjustment of the air vent as to avoid the loss of liquid. In the throttling elements between the elevated resthe operation of devices of this kind, it has been ervoir and the transmission. In the case of reshown that the liquid which passes to the res- 35 mote controlled or automatic installations, these ervoir always absorbs or entrains air. By this require special servomotor devices which increase intermingling with air, a strong transposition of the costs of installation and diminish the safety air from the transmission to the reservoir may of operation. These objections are overcome by take place, whereby an injurious under-pressure my present invention in which. the reservoir for in the transmission and a corresponding over- 40 the discharged liquid is placed entirely below the pressure in the reservoir may result. This is transm ssion, that is, the overflow edge of the undesirable for many reasons, and it is unavoidreservoir lies below the lowest point oi the movable, for instance, in such transmissions in which ing parts of the transmission, and the supply connecting conduits between the reservoir and pump for the operating liquid is also placed bethe diflerent parts or the transmission e dst, par- 45 low the reservoir. By this arrangement, it is ticularly in such cases where the conduits, for possible. in the simplest manner, to put the transcertain reasons, terminate below the liquid level mssion in operation by allowing the supply pump in the reservoir. If then there is a lower presto operate, and to place the transmission out of sure in the transmission and a higher pressure operation by stopping the pump. This feature of in the reservoir, by these pressures liquid is forced back into such parts 01' the transmission which are empty. Furthermore, such over-pressure in the reservoir makes diflicult the flow oi the returning liquid from the filled parts of the transmission which is equally undesirable and gives cause for disturbances. All 01' these objections can be avoided by providing a pressure equalizer between the air chambers of the transmission and the reservoir. The simplest embodiment provides an air connection between the highest places of the transmission and the reservoir, and such an arrangement has produced an unexpected: decrease in the loss inherent in the apparatus. Also, liquid losses from the reservoir are avoided due to the fact that pressure increase in the reservoir is avoided. Tests which have been made have demonstrated surprisingly favorable results from this improvement Preferably, the embodiment provides for the arrangement of the air connection at so high a position that liquid losses are avoided. Finally, when changing over from one part of the transmission to another part, it has been found that the discharge of air from the part to be filled with liquid and the inflow of air into the part to be emptied of the liquid,

take place much more-rapidly and more efliciently. To assist this operation, special air openlogs are provided for each part 01 the transmission, whereby an exceeding y rapid exchange of air between the transmission, the housing, and the casing, takes place. g

The fourth feature of this invention embodies an hydraulic transmission in which the pump runs with a. considerably smaller number of revolutions during the slip coupling operation than during the torque changer operation. It has been found that in the use of hydraulic transmissions, a considerably lower supply pump pressure is required to keep the slip coupling filled than is required to keep the torque changer filled with liquid. As the pump in all cases must be so designed that it can supply the necessary high pressure for the torque changer, it would work with high losses when the coupling operates. This high loss is of great importance, since the time oi. operation of the coupling constitutes bv far the greater part of the total operating time of the transmission. If the pump is a centrifugal pump, and if it is driven mechanically independently of the power shaft, for example, by a small electric motor, then the condition oi the operation can be fulfilled in accordance with the invention, without the objections named, thereby that in the operation of the slip coupling the supply pump is driven with an essentially smaller number of revolutions than is the case in the torque changer operation, and so generates the desired smaller pressure. The fact that by changing over from torque changer to the slip coupling operation, the pressure and the number of revolutions of the supply pump are reduced, can be utilized further in that this pressure difference may be used for the control of a multiple way valve, as the liquid passing from the pump to the transmission can be directed either to the slip coupling or to the torque changer. This is accomplished thereby that with the higher supply pump pressure the multiple way valve takes the torque changer position, and with the lower supply pressure pump, it takes the slipcoupling position. During the change-over from slipcoupling position to torque changer position, by increasing the supply pump pressure,'energy is stored, for instance, by compressing a spring of a servo-motor operating the multiple way valve,

position of the valve.

so that this energy is then utilized automatically to change the position 01 the valve as soon as the pump pressure is less than the force of the spring. The pressure of the supply pump depending on the number of revolutions or speed of its operating electric motor, then determines the When the higher speed is applied, the torque changer is filled, and when the lower speed is applied the slip coupling is filled.

Finally, another feature of this invention is that when the forceof power flow from the motor to the driving wheels is stopped, the various parts of the transmission are emptied oi operating liquid. In such devices it was the general desire heretofore tokeep the transmission constantly filled and special leakage-proof means were provided to keep the leakage losses and return pipes and reservoir as small as possible. In the present invention, however, the opposite path is followed whereby important advantages are obtained. It has been the endeavor of the industry to provide for heavy and medium weight vehicles, a suitable free-wheeling,..but heretofore this has not been successfully accomplished, as no one has as yet provided safely-operating, treewheeling for larger capacities. The known constructions are very complicated, sensitive, and expensive and detrimentally influence the operation. All of the advantages of free-wheeling are obtained in a simpler manner by this invention without impairing the eiliciency oi the operation. The principal underlying feature of my invention is to so operate the transmission that it may be emptied when the power flow from the motor to the driving wheels is interrupted. It is no longer necessary that such transmission be leakage-proof, 'since it may have considerable leakage and a suitable outflow oi the operating liquid may be provided in order that the transmission may be emptied rapidly. For the return of the leakage any pump will serve, the operation of which is so controlled that the above principle of operation may be carried out. of understanding. it may be assumed that the supply pump is driven by an electric motor. Suitable provision is made to empty the transmission and allow the intended tree-wheeling by switching off the control motor, the moment the power transmission from the engine to the driving wheels ceases. Such provision includes a device which makes the supply pump dependent upon the operation of the gas pedal, so that the pump in the no-load position of the gas lever does not return any liquid into the transmission. If it is again desired to transmit power to the driving wheels, by pressing down the gas pedal the supply pump motor is again switched in and the hydraulic transmission is filled thereby and power transmission is started or continues within the shortest possible time. A special advantage of such free-wheeling is that all the operating sequences follow each other without the slightest mechanical shock or annoyance, because there is no mechanical element utilized in any manner in the initiation and termination of" the power transmission. It is, moreover, in many cases desired, especially in going down-hill, to use the engine as an auxiliary brake. A mechanical freewheeling requires for this purpose, a special re turn block device, which isadifllcult, expensive, and sensitive element. In accordance with this invention, the mere filling o! the hydraulic transmission will answer this requirement. One simply switches in the supply pump motor in a ace-mos manner similar to the actuation of the return block device; and the present invention presents the advantage that for this purpose, very simple, inexpensive, and fully actuable elements are applicable. In view of the small amount of power required for the control, it is also possible without any 'difilculty to connect this switch with the will be hereinafter described, with the aid of the accompanying drawings; and the invention will be finally pointed out in the appended claims.

In the accompanying drawings:-

Figure 1 shows a side elevation of a hydraulic transmission in which the pump is at the lowest point of the liquid reservoir:

Figure 2 shows a side elevation partly in section, of another embodiment of my invention in whichall of the essential operative parts are brought within a unitary container;

Figure 3 shows a side elevation partly in section in which the apparatus shown is provided with an air vent;

Figure 4 is a diagrammatic drawing of the parts arranged in such a manner as to permit the transmission to be completely discharged of liquid after the power of the engine has been cut ofl;

Figure 5 is an enlarged drawing of parts of Fig. 4;

Figure 6 is a diagrammatic drawing of a hydraulic transmission adapted to be operated by a multiple way valve automatically controlled by the liquid pressure of the pump. whereby the supply pump runs at considerably less revolutions-per-minute when connected with the slip coupling than when connected with the torque changer; and shows diagrammatically a composite view of the various embodiments described. Figure '1 is an enlarged drawing of parts of Figure 6.

Figure 8 is a diagrammatic view similar to Figure 6 with the parts shown in position for supplying operating fluid to the torque changer.

Similar characters of reference'indicate corresponding parts throughout the various views.

Referring to Figure 7, the hydraulic transmission is contained in the casing 40, in which the slip coupling 4i and the torque changer 42 are arranged. As is known, each one of these devices consists of the driving members and the driven members. The driving members are fixedly connected with the primary or driving shaft 46, and the driven members are fixedly connected with the driven shaft 41. The driving members areindicated by 4| and 42'. and the driven members are indicated by 4i and 42". The driven members 4|" and 42' are mechanically interconnected or coupled with the driven shaft 41, by elements d, and rotate therewith. A stationary guide wheel m of the torque changer is connected by elements 11 to the casing 40.

The driving members 4 I and 42 are operatively connected by elements 9 to the driving shaft 46 and rotate therewith. When the engine 45 operates, the driving members 4| and 42 rotate with the shaft 46, while the driven members 4| and 42 and driven shaft 41 remain in rest as long as no liquid is present in the slip coupling and torque changer. As soon as operating liquid is admitted to one of these devices, either to the slip coupling 4! by means of pipe Oi or the torque changer" by means of pipe ll, then. power is transmitted tothe driven member of the respective devices through the actionof the operating liquid, so that the driven member also revolves, and operates the driven shaft 41. If it is desired to change over from one device to the other, that is, for instance, from the torque changer to the slip coupling, the liquid supply is cut oil from the torque changer and liquid is admitted to the slip coupling, by meansof pipe II.

when the supplyof liquid is cut, oil from the I torque changer, the liquid in the torque changer, dissipates, by passing out of the clearances o. The slip coupling 4| then assures the transmission of power, while the torque changer is idling. The same sequence of operation only inlthe reverse direction takes place, in the of a change-over from the slip coupling operation to the torque changer. A controlled valve 5| distributes the liquid to either the slip coupling or the torque changer, which liquid is pumped by the pump 49,'which in turn may be operated by any source of power, asfor instance; electrical means, in which case switches 84, I, I8 and 53 shown in Figure 6 are manipulated,"as will be hereinafter described.

Referring now to Figure 1,' the hydraulic transmission i0 is connected withthe discharge conduit H which in turn; is connected with the reservoir l2,*the latter being provided with an overflow edge i3,-and such edge I3 is lower than the lowest point of the operating parts of the transmission i0. At the lowest point of this res ervoiri2, a supply pump I4 is provided and this pump iscohnected with the hydraulic transmission 10 by means of the conduit I5. I

This arrangement is especially advantageous when operated in such a manner that during the starting period of the transmission the supply pump is driven with a higher numberof revolutions than that necessary to keep'the transmission filled when in normal operation. -One obtains by this a short starting period The necessary larger starting power of the supply pump is of no importance as it is required only for several seconds. In ordinary normal operation, the supply pump is required to run only with so small a number of revolutions as is necessary to main tain the transmission fllled, andtheppower re-' be passed through, and only by-Iu'rthermove ment of the switch to position He, the lower,

motor speed provided for normal operation obtained." The electric circuit is completed by conductors i8 and lid and electrical source of supply I9." Particularly important are the ad- 1 vantages of this arrangementin hydraulic transmission in which during the operation, the liquid is allowed dissipate from one part of the transmission, whereby the same is emptied, and is supplied to another part of the transmission for the purpose of filling it. Insuch a case,one uses, on the pressure sideof the supply pump, a multiple way valve, which connects piping either with the slip coupling or the torque changer parts of the transmission.

In the embodiment shown in Figure 2, the transmission, the control valve and the supply pump are all assembled in the form of one unitary self-contained unit wherein the reservoir for the liquid is made of a very simple and inexpensive vessel and is screwed onto the transmission in such a way that the pump, the control valve and all connections are enclosed by the reservoir container. In this embodiment shown in Figure 2, the conducting parts 20. 2|, and 22, the control valve 23. and the pump 24. are brought together in a unitary manner within the reservoir 26,. The pump 24 is actuated by shaft 21 of the transmission by means of the worm 2| and the worm gear 20. Thus by the operation of shaft 21, and the rotation of the worm gear 20, the worm 28 a'ndthe shaft 20 are driven. whereby the pump 24 is operated, and the liquid forced through the conduits 20, 2i and 22 suitably controlled by the valve 23. It will be noted that all 0! these operating parts are within the reservoir 26 andthat the parts are of the simplest construction. 'It will also be noted that the connections of the various conduits 20, 2| and 22 are within the liquid of the reservoir 28 so that no harm results from any leakage.

In the embodiment of Figure 3, a conduit 8| conducts operating liquid from the control valve 32 to the transmission 25.. The air spaces of the transmission 25 and of the reservoir 28 are interconnected by an air pipe 33, which through a branch pipe 34 communicates with the atmosphere at its upper end 25, this end 25 being relativciyhigh in respect to the otherparts of the apparatus in order to avoid liquid losses. The liquid is returned from the transmission to the reservoir by pipe 26. The supply pump 31 is operated by the motor 28.

In the embodiment shown in Figure 4, the engine 45 drives the shaft 41, by means of the hydraulic transmission. The engine 4! drives the primary part III of the hydraulic transmission. The secondary part of this transmission indicated by H, is secured to the shaft 41 by suitable mechanical means which are not shown and this secondary part His connected through the shaft 41 with suitable driving wheels, 41'.

The hydraulic transmission has on its exterior, discharge apertures 12 out of which, during the filling operation, liquid constantly flows ofl into the casing 13 and from this casing flow, by means of conduits I4, into the reservoir 15. Connected with the reservoir II, is a control pump 18 which again forces-or supplies the actuating liquid into the transmission by means of the pipe 11. The transmission as disclosed in Figure 4 only consists of a slip coupling. It is clear that a transmission such as that shownin Figure 4, may be used, or one in which the slip coupling cooperates with a plurality of torque changers. The pump 16 is operated by means of a very small electric motor I8, which receives its current from a battery I9 of a lighting machine ll. The automatic switch BI is connected with the gas pedal 82 so that the current flow to the motor 12 .is interrupted by the imperative position of the gas pedal, but in every other position is closed. Parallel with switch 8| are arranged a separate control switch 82, and a switch 85 operated by braking pedal 84. With the described arrangement, the operation will take place in the following manner:-

One operates the engine 46 without in any mandriving wheels 41' then takes place. After the automobile has been sufllciently accelerated and is running in a downward grade, or if it is desired for any other reason to slowly reduce the velocity, the gas supply is reduced, that is, the gas pedal 02 is raised. when it reaches its upperend position or no-load position the switch ll is opened, the electric motor 18 and the pump It stop, and the slip coupling is put out of operation due to the fact that the operating liquid is discharged from the parts I0 and II in a very short time through the discharge openings 12. Freewheeling action is thereby obtained. The reverse action takes place as soon as the gas pedal is pressed down again, feeding more gas to and speeding up the engine. when it is desired to use the engine as an auxiliary brake, either the switch 83 is closed or the braking pedal 84 is pressed downwardly a short distance. Thereby the supply pump motor 18 is again operated and the hydraulic transmission is again filled with liquid.

When the switch 82 is opened and/or when the brake 84 is released, free-wheeling again takes place until the gas pedal is again pressed downwardly. One recognizes here that with the described arrangement according to the foregoing method, the simplest and surest means for a smooth and agreeable free-wheeling is obtained and considerable savings in fuel consumption are realized, while the structural parts necessary to obtain this improvement are very inexpensive.

In the embodiment of Figure 6, the hydraulic transmission 40 consists of a hydraulic slip coupling 4| and a hydraulic torque changer 42. The

transmission is driven by an engine 45 driving] the shaft 46. The driven shaft 41 is operated.

by the transmission and actuates the driving wheels 41' through the gearing 41". The operating liquid when at rest is stored in the reservoir 48 from where it is conducted by means of the supply pump 49 through a conduit 50 and multiple way valve ll to the transmission 4!. The pump 49 is driven by an electric motor 52, the current of which is controlled by a switch 52 having a zero terminal 53 a high-speed ternrinal 53", and a low-speed terminal 52, and this electric circuit is supplied with current from any suitable source as, for instance, that indicated by the numeral 54. The multiple way valve Si is operated by means of a lever 55 which, at one end, is connected with a piston rod It or a servomotor 51. A spring It is interposed.

between the casing is and the piston ill. The valve 5! is shown in Figure 6 as connecting the conduit ill and the conduit 6| whereby the operating liquid is forced by the pump 4! into the. The lever 55 of the valve 5| slip coupling 4|. is held in this position by the spring 58, which forces the piston to the left against the liquid pressure produced by the pump, which in this case is low. If the pressure produced by the supply pump is high, due to increased speed, the

piston 60 is forced to the right, against the spring the pump 49 to the slip coupling 4|.

ape-mos tension, and the lever 99 is moved to throw the way of the valve 5| to connect the conduit 99 with conduit 9|, and disconnect conduit 9|. Thereby the liquid is forced into the torque changer 42. The operation Just above described is shown by Figure 8. The described arrangement operates in its application toautomobiles in the following manner:-.-At the standstill of the automobile, the entire transmission is emptied of its liquid. The reservoir 49 is filled, and the supply pump pipe 59 is pressureless, so that the servomotor piston 99 is pressed entirely to the left by the spring 59, whereby there is a free passage through the valve 9| for the liquid from If it is desired to set the automobile in operation, the switch 59 is set so as to cause the pump 49 running at high speed to develop high pressure in the conduit-90. Thereby the piston 90 is pressed toward the right and the multiple way valve 5| isso turned that the liquid passes through'its channel to the torque changer 42, the torque changer 42 thereby is filled, developing a torque necessary to start and accelerate the automobile. When it is desired to change over to the slip coupling operation, the switch 99 is set for the lower speed of the pump motor 92. Thereby pressure in the conduit 50 is decreased, the spring 58 presses the piston 90 to the left and the channel of the valve 5| is placed in alignment with the conduits 50 and 9| leading to the slip coupling 4|. The described arrangement may be advantageously installed in automotive vehicles and adapted to the well-known control devices of such vehicles in a very simple manner. This may be carried out by so arranging the switch 53 in a circuit with the gas pedal switch 94' and the braking pedalswitch 65. When both pedals 94 and 99 are in their upper-end positions the current is interrupted. For the purpose of putting the automobile in operation, once its engine is running and the switch 99 is in contact with pedal 95, the current will be againswitched on in which case the switch 53 can be in either position 59'' or 59, whereupon the pump 49 will fill either the slip coupling 4| or, the torque changer 42, and the engine will then be operative as an auxiliary brake. Hence, depending upon the position of the switch 59, either the slip coupling 4|, or the torque changer 42, is used as a brake.

My invention may be used in connection with a hydraulic slip coupling as shown in Fig. 5. The structure shown in Fig. '7, has at its left hand side, a hydraulic slip coupling and at its right hand side a torque changer. The invention described herein finds-its embodiment, first, in such a hydraulic slip coupling, secondly, in such a torque changer, and thirdly in the combi nation of a hydraulic slip coupling and a torque changer. As heretofore stated, one or more torque changers can be used.

The invention also comprises the novel methods hereinbefore described.

pump, and put out of operation by the stopping of the same, said operation of the supply pump and non-operation of the same taking placeduring the rotation of the primary shaft and means for the starting operation and vthe stopping of the pump, the stopping of the pump being independent of the primary shaft.

2. In a hydraulic variable speed transmission having a slip coupling and a torque changer, a supply pump for supplying operating liquid to the transmission, a motor for the same having -more than one speed, the higher one of said speeds being adapted to effect the operation of the pump to fill the transmission with operating liquid having a fiow velocity of the liquid corresponding to such higher speed, and means for normally operating the motor at the other speed and operative only after first operating the motor and pump at the higher speed, whereby the filling time of the transmission is decreased to obtain a quick start.

3. In a hydraulic variable speed transmission having a casing, a slip coupling and a torque changer in said casing. a pump for forcing the operating liquid to either the slip coupling or to the torque changer, and a multiple way valve for guidingthe liquid from the pump to either the slip coupling or to the torque changer a reservoir, supply pipe leading from the reservoir to the multiple way valve and a separate pipe from the casing for discharging the liquid to the reservoir.

4. In a hydraulic variable speed transmission, consisting of a slip coupling and a torque changer, a pump for forcing the operating liquid to either the slip coupling or to the torque changer, a multiple way valve for guiding the liquid to either the slip coupling or to the torque changer, and a servomotor for operating the valve, a supply pipe for the servomotor connected directly to the supply pipe of the multiple way valve.

5. In a hydraulic variable speed transmission consisting of two or more liquid circuits of which one may be a slip coupling and the other a torque changer, a supply pump, a multiple way valve,

a control switch for the pump, means operating the multiple way valve depending upon the position of the control switch, and means operat-- ing the supply pump at an increased speed during the filling period of the liquid circuit when starting or when changing from one circuit to higher speed when connected with the torque changer.

7. In a hydraulic variable speed transmission having a slip coupling and a torque changer adapted to be put into operation by filling the slip coupling or torque changer with liquid d put out of operation by emptying the slip coupling or torque changer of liquid, a supply pump, a multiple way valve, means connecting the same with the pump and with the slip coupling and torque changer, and means interposed in said connecting means operating the multiple way valve by the higher pressure necessary for the operation of the pump when operating the torque l5 changer..

8. In a hydraulic variable speed tron consisting of a slip coupling and a torque changer,- adapted to be put in operation by filling the same with liquid and put out of operation by emptying the same of liquid, a supply pump, a multiple way valve, means storing energy during the switching of the multiple way valve from slip coupling position to torque changer position, and means utilizing said energy for the reverse movement from torque changer operation to slip coupling operation, eifected by the reduction of the speed of the supply pump, which in turn decreases the liquid pressure, whereby the position of the multiple way valve from the torque changer position to the slip coupling position, is

changed.

9. In a hydraulic variable speed transmission, a coupling, a pump for forcing liquid into the coupling, a motor for the pump, a speed switch for operating the motor at dmerent speeds for operating the pump at diiferent speeds, electrical connections connecting the motor of the pump, switch, and source of supply, a gas pedal switch in said electrical circuit, a braking pedal switch in said electrical circuit, and electrical means connecting the gas pedal and braking pedal switches with the motor of the pump, for operating the motor and the pump by'closing either the gas pedal switch or the braking pedal switch to operate the coupling.

10. In a hydraulic variable speed transmission for motor vehicles, a slip coupling and a torque changer, a pump for optionally forcing liquid into either the slip coupling or the torque changer, a

motor for the pump, an electric circuit connected with the motor, a gas pedal switch in said electric circuit and associated with the vehicle, a

brake pedal switch in said electric circuit and associated with the vehicle, and a third switch for said electric circuit for cutting out the motor and switching in the motor independently 'of the brake pedal switch and the gas pedal switch, said pump motor being adapted to be operated by either of the gas pedal switch or brake pedal switch or third switch independently of each said last named electrical circuit, a braking pedal switch in said electrical circuit, and a fourth switch in said electrical circuit, said fourth switch being adapted to be closed to close the circuit when the gas pedal switch and brake pedal switch are open, said fourth switch being open when it is desired to operate either'the gas pedal switch or the brake pedal switch, and the speed switch being adapted tooperate the motor which operates the pump at diiierent speeds whether the fourth switch is closed or whether 5 either the gas pedal switch or the brake pedal switch closes the circuit.

12. A hydraulic transmission for automotive vehicles comprising a prime mover, 'a primary shaft, a secondary shaft. a primary wheel, a sec- 10 ondary wheel,- said primary and secondary wheels being interposed between the primary and secondary shafts, a supply pump for supplying working fluid between the primary ahd secondary wheels, a motor for the supply pump, an electric ll circuit for the motor, operable independent of the prime mover, means for energizing the independent electric circuit, for operating the meter and means for stopping the motor and the pump, the stopping ofthe pump operating independent 50 of the primary shaft and when the pump has stopped interrupting the supply of the working fiuid between the primary and secondary wheels, whereby the pump alone controls the supply of such working fluid. l

13. In an hydraulic variable speed transmission adapted for automotive vehicles having an engine and driving wheels, said tra on including primary and secondary whbels and an interposed fluid, which is adapted to\be put into 30 operation by filling the same with the fluid and put out of operation by emptying the same of the fiuid, the combination of means for controlling the operation of the engine, means for controlling the filling and emptying the transmission of the fiuid, and means connecting the engine, the transmission, and the driving'wheels, whereby the control means of the engine upon eii'ecting discontinuance of the transmission of power from the engine to the driving wheels, 40 causes the control means of the tron to empty the same, independently of the rotation of the engine.

14. In an hydraulic variable speed transmission adapted for automotive vehicles having an 4| engine'and driving wheels, said transmission including primary and secondary wheels and an interposed fiuid, which transmission is adapted to be put into operation by the filling of the same with the fluid and to he put out of operation by 50 emptying the same of the fluid, the combination of means for controlling the operation of the engine, means for controlling the filling and emptying the transmission of the fluid, means connecting the engine, the transmission, and 56 driving wheels, independent means for filling with fiuidthe space between the primary and secondary wheels independently of the operation of the aforesaid two control means, and means to operate said independent fliling means, whereby after 00 the control means of the engine has effected the discontinuance of the transmission of power from the engine to the driving wheels and after the control means of the transmission has operated to empty the tion to enable free wheeling 05 to take place, the independent filling means may be operated to fill the transmission with the fluid while the engine is idling, to effect a reverse flow of power from the driving wheels to the engine and brake the vehicle through the medium of the 70 engine.

15. In an hydraulic variable speed transmission for vehicles, which transmission has continuously open discharge apertures, a primary shaft with primary wheels thereon. a secondary shaft 75 with secondary wheels thereon, a pump for supplying the operating liquid to the space formed between each pair of primary and secondary wheels, for effecting the transmission of power from the primary to the secondary shaft by filling the space between the primary and secondary wheels on the starting of the pump and maintaining such filling during the continued operation of the pump, whereby operation or non- 10 operation of the pump alone determines the operation of the transmission independent of the primary shaft, and means for operating the pump including both the starting and stopping of the same, said stopping of the pump being independent of the primary shaft, and interrupting the transmission of power from the primary shaft to the secondary shaft by interrupting the flow of the operating liquid filling the space between the primary and secondary wheels.

ERNST SEIBOLD. 

